Abstract: A constant-amplitude and continuous-phase modulation method for modulating digital data and for demodulating said modulated signal, said data taking the form of symbols a(n) that can take a number M of states at least equal to 2, the method including, in transmission, use of a voltage-controlled oscillator (VCO) for which the control is the sum of pulses he(a(n), t?n T), the form and the amplitude of which depends on the value of a(n); and, in reception, use of a single impulse response filter C0(t) regardless of the value of M in transmission, said functions he and C0 having a number of parameters that are optimized in the design of the system in order to obtain at the output of the filter C0 a constellation that is as close as possible to the theoretical constellation.

Abstract: A constant-amplitude and continuous-phase modulation method for modulating digital data and for demodulating said modulated signal, said data taking the form of symbols a(n) that can take a number M of states at least equal to 2, the method including, in transmission, use of a voltage-controlled oscillator (VCO) for which the control is the sum of pulses he(a(n), t?n T), the form and the amplitude of which depends on the value of a(n); and, in reception, use of a single impulse response filter C0(t) regardless of the value of M in transmission, said functions he and C0 having a number of parameters that are optimized in the design of the system in order to obtain at the output of the filter C0 a constellation that is as close as possible to the theoretical constellation.

Abstract: A system and method for estimating and tracking the frequency offset for a transmission system whose bandwidth is not insignificant with respect to the central frequency, the system transmitting a waveform including fixed carriers whose level is substantially greater than that of the carriers transporting the information, the carriers having frequencies F0 . . . FN-1, and the useful signal carrying the information. The system has N banks (100) of band-pass filters with, each bank having P filters, suitable for covering all of the values that the frequencies F0 . . . FN-1 may take after Doppler offset. A filter output is connected to a quadratic envelope detector. P adders (200) are suitable for adding the corresponding outputs of the N banks of filters. A system (300) detects the position of the two largest maxima from the P sums and validates the position of the largest maximum. A system (400) stores the positions of the two largest maxima and their “weight” and for predicting the current value.

Abstract: A method for transmitting data is disclosed having the following steps: emitting packets of at least two types: pure data (long packets) and acknowledgments of receipt (acknowledgment) (short packets). Each packet is formed of three components: a—an acquisition preamble, (1) for presence detection and the joint determination of the initial values of the time shift and of the frequency shift, and b—the data proper, (2) and c—a set of unmodulated fixed carriers (3) making it possible to permanently estimate the frequency shift.

Abstract: A method for transmitting data is disclosed having the following steps: emitting packets of at least two types: pure data (long packets) and acknowledgments of receipt (acknowledgment ) (short packets). Each packet is formed of three components: a—an acquisition preamble, (1) for presence detection and the joint determination of the initial values of the time shift and of the frequency shift, and b—the data proper, (2) and c—a set of unmodulated fixed carriers (3) making it possible to permanently estimate the frequency shift.

Abstract: Method and system adapted to modifying an audio signal or speech signal comprising a step in which the frequency spectrum S(k) of the signal is converted by the application of a non-linear function. The method comprises at least the following steps: firstly, determining the signal level A(k), B(k) associated with a frequency k by taking account of different levels a(k), b(k) of the signal for the frequency k concerned and/or the neighboring frequencies (step 2a, step 8a); secondly, applying the non-linear function to said level A(k), B(k).

Abstract: A system and method for estimating and tracking the frequency offset for a transmission system whose bandwidth is not insignificant with respect to the central frequency, the system transmitting a waveform including fixed carriers whose level is substantially greater than that of the carriers transporting the information, the carriers having frequencies F0 . . . FN-1, and the useful signal carrying the information. The system has N banks (100) of band-pass filters with, each bank having P filters, suitable for covering all of the values that the frequencies F0 . . . FN-1 may take after Doppler offset. A filter output is connected to a quadratic envelope detector. P adders (200) are suitable for adding the corresponding outputs of the N banks of filters. A system (300) detects the position of the two largest maxima from the P sums and validates the position of the largest maximum. A system (400) stores the positions of the two largest maxima and their “weight” and for predicting the current value.

Abstract: A device and a method for the rejection of interference in a payload signal are described. The method includes evaluating the interference phase and evaluating the instantaneous amplitude of the interference by the least error squares method, forming a ratio r=(B2/(A2+B2)) where A is the real part of the amplitude of the interference and B is the complex part of the amplitude of the interference. If r is below the threshold value r0, the signal is corrected by replacing the central sample of the signal by a weighted sum moderated by the central sample and neighboring samples.

Abstract: A system and method for transmitting an analog signal. The analog signal is converted into complex numbers such that two successive audio samples respectively form a real part and an imaginary part of a respective complex number. The complex numbers are then dispersed in a time-frequency space. The complex numbers are then modulated through a digital modulator into temporal signals and the temporal signals are output for transmission. Thereby, a digital modulator conventionally used for modulating digital input signals can operate for the transmission of an analog signal.

Abstract: A method and device are disclosed for the detection and synchronization of a signal in a frequency-hopping system. The method has a step, for each frequency F(1) . . . F(M), of selecting the K samples corresponding to the greatest values of the signal, and their positions. For a given position, the M greatest values are combined which are selected from among K samples on each frequency having the given position. The greatest combined value is kept and the corresponding position. The greatest combined value is compared with a threshold value, and if the greatest combined value is greater than this threshold value, then the detection of the signal is declared.

Abstract: A method and device to equalize a signal received by a receiver after having traveled through a transmission channel, the signal including one data block and several probes located on either side of the data block. The method includes a step in which the impulse response of the channel is estimated before and after a data block n in taking account of the probes (Probe n 1 and Probe n) located on either side of the data block n and also of the probes that precede and follow the Probes n?1 and Probe n, the probes being weighted and combined with one another.

Abstract: A system and method to provide continuity of service in a radio broadcasting system, wherein the radio broadcasting system includes at least one modem using the COFDM technique, and transmits N time-frequency cells modulated independently of one another. A number N1 of cells conveying digital audio signal S1 and a number N2 of cells conveying analog audio signal S2 are transmitted to a receiver. When the receiver cannot decode the signal in the N1 cells, the receiver replaces the digitized audio signal S1 with the analog signal S2.

Abstract: A short wave high efficiency radio broadcasting transmitter for digital transmissions. The transmitter includes a power tube in which the grid is excited by a variable phase signal through an excitation device and in which the anode is amplitude modulated by the output signal from a modulator. The phase and amplitude signals applied to the grid and anode of the tube respectively represent the phase and amplitude of the complex signal to be transmitted. The amplification characteristic of the excitation device remains linear for low amplitudes of the signal to be transmitted and operates under saturated conditions when the amplitude of the signal to be transmitted exceeds a given threshold value, so that the amplification characteristic of the transmitter as a whole remains linear independently of the amplitude of the signal to be transmitted. Such a transmitter may find particular application as a short wave transmitter.

Abstract: A device and a method for the rejection of interference in a payload signal are described. The method includes evaluating the interference phase and evaluating the instantaneous amplitude of the interference by the least error squares method, forming a ratio r=(B2/(A2+B2)) where A is the real part of the amplitude of the interference and B is the complex part of the amplitude of the interference. If r is below the threshold value r0, the signal is corrected by replacing the central sample of the signal by a weighted sum moderated by the central sample and neighboring samples.

Abstract: A method and device for the detection and synchronization of a signal in a frequency-hopping system, the method comprising at least the following steps: for each frequency F(1). . . F(M), selecting the K samples corresponding to the greatest values of the signal, and their positions; combining, for a given position, the M greatest values selected from among K on each frequency having said position, and keeping the greatest combined value and the corresponding position; comparing the greatest combined value with a threshold value, and if it is greater than this threshold value, then declaring the detection of the signal.

Abstract: A process for neutralizing a tube of a high power digital radio broadcasting transmitter includes modulating two quadrature signals I(t), Q(t) at a transmission frequency (F0) by a modulator to control a grid of the tube which is configured to work at saturation with a gain V2. A phase-modulated input signal E(t) output from the modulator is amplified by an amplifier which is configured to work at saturation with a gain V1. The input signal E(t) is predistorted by digital means so as to compensate for an undesirable coupling between an anode and the grid of the tube of the transmitter so that an output of the transmitter corresponds to a desired output signal S(t). A corrector signal W(t) is calculated using the expression W(t)=jg(t)S(t).

Abstract: A process for the construction of LDPC codes including N symbols, of which K are free, each code being defined by a check matrix A including M=N−K rows, N columns, and t nonzero symbols in each column. The method includes allocating the same number of nonzero symbols to all the rows of the check matrix A, taking t to be the smallest possible odd number, defining the columns of A such that any two columns of the check matrix A have at most one nonzero value in a common position, and defining the rows of A such that any two rows of the check matrix A have only one nonzero value in a common position.

Abstract: A system for the estimation of the complex gain of a transmission channel is designed for parallel type modulators/demodulators that can be used in digital radio broadcasting. The system includes a given number N of sets of interpolators to estimate the gain on a useful symbol from known symbols constituting gain references evenly positioned in the transmitted signal, each set of interpolators being adapted to a particular situation of reception, ranging from a stable single-path channel to a channel with high temporal dispersion and high instability. The outputs of the interpolators are coupled to a selection device programmed to choose the set of interpolators that gives the weakest estimated noise during a specified length of time. Such a system may find application to digital radio transmission.

Abstract: A method and device for the equalization of data in a receiver, the data having traveled through a transmission channel, the received signal comprising one or more frames. The method determines at least one fictitious probe in the data block by using at least one part of the probes available in the frames before and after the frame considered. It also comprises a step for determining the intermediate impulse response associated with the fictitious probe or probes and the combination of said intermediate impulse responses.

Abstract: A method and device to equalize a signal received by a receiver after having traveled through a transmission channel, said signal comprising at least one data block and several probes located on either side of the data block. The method comprises at least one step in which the impulse response of the channel is estimated before and after a data block n in taking account of the probes (Probe n−1 and Probe n) located on either side of the data block n and also of the probes that precede and follow the Probes n−1 and Probe n, said probes being weighted and combined with one another.